A turbomachine is a device that adds or extracts energy to or from a fluid stream through dynamic interactions between the fluid stream and a rotating rotor of the turbomachine. The rotor typically includes a hub to which are coupled a plurality of blades. One factor influencing the dynamic interactions between the fluid stream and the rotating rotor, and thus the performance of the turbomachine, is the blade pitch angle of each one of the blades. For a given blade, the blade pitch angle is the angle between a chord of a section of the blade and a line perpendicular to an axis of rotation of the rotor.
One type of turbomachine is an axial-flow fan. An axial-flow fan typically includes a rotor disposed in a housing and coupled to a motor operative for rotating the rotor. Through rotation of its rotor, an axial-flow fan is operative to produce currents in order to circulate, exhaust, or deliver volumes of a gas such as air. As mentioned previously for turbomachines in general, one factor influencing the dynamic interactions between the gas and the axial-flow fan's rotating rotor, and thus the performance of the axial-flow fan, is the blade pitch angle of each one of the blades of the axial-flow fan's rotor.
Existing rotors for axial-flow fans suffer from multiple drawbacks. One of these drawbacks is that, typically, the coupling means by which a blade of an existing rotor is coupled to the rotor's hub is also the sole means directed to maintaining the blade pitch angle of the blade at a given value.
When an axial-flow fan including such an existing rotor is in operation over an extended period of time, dynamic effects such as vibrations experienced by the rotating rotor can affect the coupling between the blades and the hub of the rotor, and can thus lead to undesired variations of the blade pitch angle of the blades. Such undesired variations usually lead to less than optimal performance of the axial-flow fans including existing rotors. For instance, frequent and inconvenient interruptions of the operation of an axial-flow fan including such an existing rotor may be required in order to periodically adjust the blade pitch angle of the blades of the rotor, which continually drifts from its desired value under operation of the axial-flow fan.
Accordingly, there is a need for improvements in rotors for turbomachines and, in particular, for improvements directed to at least partly inhibiting undesired variations of the blade pitch angle of the blades of a rotor.